/*******************************************************************************
 * Copyright 2011 See AUTHORS file.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ******************************************************************************/

package com.badlogic.gdx.physics.box2d.joints;

import com.badlogic.gdx.math.Vector2;
import com.badlogic.gdx.physics.box2d.Body;
import com.badlogic.gdx.physics.box2d.JointDef;

/**
 * Distance joint definition. This requires defining an anchor point on both bodies and the non-zero length of the distance joint.
 * The definition uses local anchor points so that the initial configuration can violate the constraint slightly. This helps when
 * saving and loading a game.
 *
 * @warning Do not use a zero or short length.
 */
public class DistanceJointDef extends JointDef {
    /**
     * The local anchor point relative to body1's origin.
     */
    public final Vector2 localAnchorA = new Vector2();
    /**
     * The local anchor point relative to body2's origin.
     */
    public final Vector2 localAnchorB = new Vector2();
    /**
     * The natural length between the anchor points.
     */
    public float length = 1;
    /**
     * The mass-spring-damper frequency in Hertz.
     */
    public float frequencyHz = 0;
    /**
     * The damping ratio. 0 = no damping, 1 = critical damping.
     */
    public float dampingRatio = 0;

    public DistanceJointDef() {
        type = JointType.DistanceJoint;
    }

    /**
     * Initialize the bodies, anchors, and length using the world anchors.
     */
    public void initialize(Body bodyA, Body bodyB, Vector2 anchorA, Vector2 anchorB) {
        this.bodyA = bodyA;
        this.bodyB = bodyB;
        this.localAnchorA.set(bodyA.getLocalPoint(anchorA));
        this.localAnchorB.set(bodyB.getLocalPoint(anchorB));
        this.length = anchorA.dst(anchorB);
    }
}
